Preparation of oyster flesh extracts

ABSTRACT

The invention relates to the preparation of oyster flesh extracts. Raw oyster flesh is placed in an extractor with a solution stored in it. The extractor is closed up tight and pressurized to 1 atm or higher to extract oyster flesh extracts from the raw oyster flesh, and they are fed into the solution in the extractor. An extraction solution with the oyster flesh extracts fed in it is concentrated. An alcohol solution is added to the concentrated solution to precipitate out the oyster flesh extracts. The precipitates are dried into dry oyster flesh extracts.

ART FIELD

The present invention relates to a method of preparing oyster fleshextracts by concentration and precipitation, which ensures efficientextraction of oyster flesh extracts from oyster flesh such as raw oysterflesh, and efficient collection of them in larger amounts withoutdeterioration by heat denaturation in useful effective components inthose extracts.

BACKGROUN ART

In recent years, oyster flesh extracts have commanded a lot more growingattention as impeccable health-food supplements containing moreeffective substances.

Thus, there are now commercially available health-food supplements basedon oyster flesh extracts extracted by a variety of extraction methods.In this regard, for instance, see JP(A)10-136946.

For the extraction of such oyster flesh extracts, on the other hand, itis still desired to have an efficient method of obtaining oyster fleshextracts containing large amounts of nutrient sources such as glycogens,taurine and proteins, and so-called platelet-aggregation inhibitionsubstances such as zinc.

SUMMARY OF THE INVENTION

Such being the case, the primary object of the invention is to provide amethod of preparing oyster flesh extracts with an improved degree ofextraction, which contain ever larger amounts of useful nutrient sourcessuch as taurine, glycogens and proteins, so-called platelet-aggregationinhibition substances such as zinc and selenium, and other usefulsubstances such as vitamins.

Thus, the present invention provides a method of preparing oyster fleshextracts, characterized by comprising:

an extraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and pressurizing saidraw oyster flesh to 1 atm or higher to extract oyster flesh extractsfrom said raw oyster flesh in a pressurized state, and feeding saidoyster flesh extracts into said solution in said extractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts.

The invention also provides a method of preparing oyster flesh extracts,characterized by comprising:

-   -   a first extraction step of placing raw oyster flesh in an        extractor with a solution stored therein, and putting said raw        oyster flesh in a normal pressure state in said extractor to        extract a portion of oyster flesh extracts from said raw oyster        flesh, and feeding said portion of oyster flesh extracts into        said extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a second extraction step of again placing said raw oyster flesh used insaid first extraction step in an extractor with a solution storedtherein, pressurizing said raw oyster flesh to 1 atm or higher in saidextractor to extract another portion of oyster flesh extracts from saidraw oyster flesh in a pressurized state, and feeding said anotherportion of oyster flesh extracts in an extraction solution,

a second concentration step of concentrating said extraction solutionwith said another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step to precipitate out saidanother portion of oyster flesh extracts, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

an extraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and putting said rawoyster flesh under a reduced pressure of 1 atm or lower to extractoyster flesh extracts from said raw oyster flesh in a reduced-pressurestate, and feeding said oyster flesh extracts into said solution in saidextractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a first extraction step of placing raw oyster flesh in an extractor witha solution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into an extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a second extraction step of again placing said raw oyster flesh used insaid first extraction step in an extractor with a solution storedtherein, putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract another portion of oyster fleshextracts from said raw oyster flesh in a reduced-pressure state, andfeeding said another portion of oyster flesh extracts in said extractionsolution,

a second concentration step of concentrating said extraction solutionwith said another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step to precipitate out saidanother portion of oyster flesh extracts, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a selective extraction step of selecting either a pressure extractionstep of placing raw oyster flesh in an extractor with a solution storedtherein, closing up said extractor and pressurizing said raw oysterflesh to 1 atm or higher to extract oyster flesh extracts from said rawoyster flesh in a pressurized state or a reduced-pressure extractionstep of putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state,

a feed step of extracting oyster flesh extracts from said raw oysterflesh in either said pressure extraction step or said reduced-pressureextraction step, and feeding said oyster flesh extracts into saidsolution in said extractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a first extraction step of placing raw oyster flesh in an extractor witha solution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into said extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a selective extraction step of selecting either a pressure extractionstep of again placing said raw oyster flesh used in said firstextraction step in an extractor with a solution stored therein, andpressurizing said ray oyster flesh to 1 atm or higher in said extractorto extract another portion of oyster flesh extracts from said raw oysterflesh in a pressurized state or a reduced-pressure extraction step ofputting said raw oyster flesh under a reduced pressure of 1 atm or lowerin said extractor to extract another portion of oyster flesh extractsfrom said raw oyster flesh in a reduced-pressure state,

a second feed step of feeding said another portion of oyster fleshextracts obtained in either said pressure extraction step or saidreduced-pressure extraction step into an extraction solution,

a second concentration step of concentration said extraction solutionwith said another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

an extraction step of placing raw oyster flesh in an extractor with asolution stored therein, extracting oyster flesh extracts from said rawoyster flesh in said extractor, and feeding said oyster flesh extractsinto said solution in said extractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts, wherein:

in said concentration step, said extraction solution is put under areduced pressure of 1 atm or lower and concentrated by low-temperatureheating in a reduced-pressure state, and

in said precipitation step, said alcohol solution is added to saidconcentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

an extraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and pressurizing saidraw oyster flesh to 1 atm or higher to extract oyster flesh extractsfrom said raw oyster flesh in a pressurized state, and feeding saidoyster flesh extracts into said solution in said extractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts, wherein:

in said concentration step, said extraction solution is put under areduced pressure of 1 atm or lower and concentrated by low-temperatureheating in a reduced-pressure state, and

in said precipitation step, said alcohol solution is added to saidconcentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a first extraction step of placing raw oyster flesh in an extractor witha solution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into said extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a second extraction step of again placing said raw oyster flesh used insaid first extraction step in an extractor with a solution storedtherein, pressurizing said raw oyster flesh to a pressure of 1 atm orhigher in said extractor to extract another portion of oyster fleshextracts from said raw oyster flesh in a pressurized state, and feedingsaid another portion of oyster flesh extracts in said extractionsolution,

a second concentration step of concentrating an extraction solution withsaid another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step to precipitate out saidanother portion of oyster flesh extracts, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts, wherein:

in each of said concentration steps, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and

in each of said precipitation steps, said alcohol solution is added tosaid concentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

an extraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and putting said rayoyster flesh under a reduced pressure of 1 atm or lower to extractoyster flesh extracts from said raw oyster flesh in a reduced-pressurestate, and feeding said oyster flesh extracts into said solution in saidextractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts, wherein:

in said concentration step, said extraction solution is put under areduced pressure of 1 atm or lower and concentrated by low-temperatureheating in a reduced-pressure state, and

in said precipitation step, said alcohol solution is added to saidconcentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a first extraction step of placing raw oyster flesh in an extractor witha solution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into an extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a second extraction step of again placing said raw oyster flesh used insaid first extraction step in an extractor with a solution storedtherein, putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract another portion of oyster fleshextracts from said raw oyster flesh in a reduced-pressure state, andfeeding said another portion of oyster flesh extracts in said extractionsolution,

a second concentration step of concentrating said extraction solutionwith said another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step to precipitate out saidanother portion of oyster flesh extracts, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts, wherein:

in each of said concentration steps, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and

in each of said precipitation steps, said alcohol solution is added tosaid concentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a selective extraction step of selecting either a pressure extractionstep of placing raw oyster flesh in an extractor with a solution storedtherein, closing up said extractor and pressurizing said raw oysterflesh to 1 atm or higher to extract oyster flesh extracts from said rawoyster flesh in a pressurized state or a reduced-pressure extractionstep of putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state,

a feed step of extracting oyster flesh extracts from said raw oysterflesh in either said pressure extraction step or said reduced-pressureextraction step, and feeding said oyster flesh extracts into saidsolution in said extractor,

a concentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein,

a precipitation step of adding an alcohol solution to a solutionconcentrated in said concentration step to precipitate out said oysterflesh extracts, and

a formation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts, wherein:

in said concentration step, said extraction solution is put under areduced pressure of 1 atm or lower and concentrated by low-temperatureheating in a reduced-pressure state, and

in said precipitation step, said alcohol solution is added to saidconcentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

Further, the invention provides a method of preparing oyster fleshextracts, characterized by comprising:

a first extraction step of placing raw oyster flesh in an extractor witha solution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into said extraction solution,

a first concentration step of concentrating said extraction solutionwith said portion of oyster flesh extracts fed therein,

a first precipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts,

a first formation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts,

a selective extraction step of selecting either a pressure extractionstep of again placing said raw oyster flesh used in said firstextraction step in an extractor with a solution stored therein, andpressurizing said raw oyster flesh to 1 atm or higher in said extractorto extract another portion of oyster flesh extracts from said raw oysterflesh in a pressurized state or a reduced-pressure extraction step ofputting said ray oyster flesh under a reduced pressure of 1 atm or lowerin said extractor to extract another portion of oyster flesh extractsfrom said raw oyster flesh in a reduced-pressure state,

a second feed step of feeding said another portion of oyster fleshextracts obtained in either said pressure extraction step or saidreduced-pressure extraction step into an extraction solution,

a second concentration step of concentration said extraction solutionwith said another portion of oyster flesh extracts fed therein,

a second precipitation step of adding an alcohol solution to a solutionconcentrated in said second concentration step, and

a second formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts, wherein:

in each of said concentration steps, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and

in each of said precipitation steps, said alcohol solution is added tosaid concentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.

ADVANTAGES OF THE INVENTION

According to the oyster flesh extract preparation method of theinvention using a reduced-pressure, low-temperature heatingconcentration process, it is possible to obtain oyster flesh extractswith improved efficiency, which contain ever larger amounts of usefulnutrients such as glycogens, taurine and proteins, platelet-aggregationinhibition substances such as zinc, and other helpful substances.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a table illustrative of the (theoretical) contents of traceelements in 100 g of dry matter, and the weight of dry matter preparedfrom 20 kg of raw oysters, in the case of pressure extraction.

FIG. 2 is a table illustrative of the (theoretical) contents of traceelements in 100 g of dry matter, and the weight of dry matter preparedfrom 20 kg of raw oysters, in the case of reduced-pressure extraction.

FIG. 3 is a table illustrative of the contents of trace elements in 100g of dry matter in the case of normal-pressure heating concentration,and reduced-pressure, low-temperature heating concentration.

BEST MODE OF CARRYING OUT THE INVENTION

The present invention is now explained with reference to its preferableembodiments.

(1) Pressure Extraction of Oyster Flesh Extracts

First, there is provided a so-called hemi-spherical extractor with wateror other solution stored therein. Then, chucked raw oyster flesh iscarefully placed in the extractor as it is, that is, without beinggrounded.

Subsequently, the extractor is closed up tight, and pressure is appliedto the oyster flesh.

By way of illustration but not by way of limitation, a pressure of 1 atm(0.1 megapascal) or higher is applied, although a pressure of about 1.1atm (0.11 megapascal) to about 2.5 atm (0.25 megapascal) is preferred.How long the flesh is pressurized is also not critical, although apressurization time of about 5 minutes to about 60 minutes is preferred.The temperature is then held at 75° C. to 120° C., and pressurization isaccompanied by temperature rises.

During the extraction, it is not necessary to carry out stirring in sucha way as to do no damage to the shucked oyster flesh, because efficientextraction is achievable without recourse to agitation according to theinvention.

In this way, various effective components are efficiently extracted fromthe oyster flesh, and they are then efficiently dissolved in an aqueoussolution in the extractor.

The amount of the extracts obtained is found to be much more increasedthan that extracted under normal pressure. The extraction time, too, isfound to be shorter than that applied in conventional manners.

Then, the solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

How to concentrate the aqueous solution is not critical; concentrationmay be carried out in such a way as to enable the extracted oyster fleshextracts to have a solid matter content of, for instance, about 15 to 45(W/W)%.

Concentration operation may ordinarily be carried out at an elevatedtemperature, for instance, in the range of 60° C. to 70° C. or evenhigher. If a reduced-pressure, low-temperature concentration process isused, the concentration operation can then be done at lowertemperatures.

As already mentioned, how to concentrate the aqueous solution is notcritical; use may be made of not only the reduced-pressure,low-temperature concentration but also heating concentration at normaltemperature, concentration by membrane, pressurizing/heatingconcentration or the like.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is stirred and allowed to standfor a given period of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

Thus, the present invention can provide a method of extracting andpreparing, with an improved degree of extraction, oyster flesh extractsthat contain taurine, glycogens and proteins, so-calledplatelet-aggregation inhibition substances containing zinc, vitamins,and other helpful substances at increased rates.

The invention is now explained with reference to FIG. 1.

As shown at No. 1 in FIG. 1, with conventional normal-pressureextraction, that is, when extraction operation was performed at 1 atm(0.1 megapascal) for 80 minutes, the extracts were found to contain 24.4mg of Zn, 125.4 μg of Se, 4.22 mg of Fe and 4.73 mg of Cu per 100 grams,and 772.2 g of dried matter providing oyster flesh extracts werecollected from 20 kg of shucked raw oyster flesh used.

On the other hand, with the pressure extraction, that is, whenextraction operation was performed at a pressure of 1.5 atm (0.15megapascal) for 20 minutes, the extracts were found to contain 27.74 mgof Zn, 108.6 μg of Se, 3.87 mg of Fe and 3.67 mg of Cu per 100 grams,and 958.5 g of dried matter providing oyster flesh extracts werecollected from 20 kg of raw oyster flesh used. Thus, there was asignificant quantitative increase.

Further, when extraction operation was effected under an increasedpressure, i.e., at 1.5 atm (0.15 megapascal) for 40 minutes, theextracts were found to contain 27.74 mg of Zn, 108.6 μg of Se, 3.87 mgof Fe and 3.67 mg of Cu per 100 grams, and 1,054.8 g of dried matterwere obtained from 20 kg of raw oyster flesh used.

Furthermore, when extraction operation was done under a more increasedpressure, i.e., at 2 atm (0.2 megapascal) for 20 minutes, the extractswere found to contain 23.2 mg of Zn, 111.7 μg of Se, 2.87 mg of Fe and3.38 mg of Cu per 100 grams, and 956.9 g of dried matter were obtainedfrom 20 kg of raw oyster flesh used.

In addition, when extraction operation was done under an increasedpressure, i.e., at 2 atm (0.2 megapascal) for 30 minutes, the extractswere found to contain 22.3 mg of Zn, 103.9 μg of Se, 3.17 mg of Fe and4.49 mg of Cu per 100 grams, and 943.3 g of dried matter were obtainedfrom 20 kg of raw oyster flesh used.

The so-called double extraction process wherein one portion of oysterflesh extracts is extracted from raw oyster flesh and another portion isthen extracted from the same raw oyster is now explained.

First, oyster flesh extracts are extracted from raw oyster flesh in theso-called normal pressure state, i.e., at 1 atm (0.1 megapascal) in thesame extractor as already mentioned.

This extraction, referred to as normal-pressure extraction, is carriedout for a period of time of, for instance, 80 minutes to 120 minutes.

The temperature of the solution is not critical; a temperature of about50° C. to about 80° C. is usually preferred, although temperature oflower than 50° C. or higher than 80° C. could be used.

The raw oyster flesh extracts extracted at the normal pressure are fedback into the aqueous solution in the extractor to obtain an aqueoussolution in which they are dissolved.

Then, that aqueous solution is concentrated. How to concentrate theaqueous solution is not critical; concentration may be carried out insuch a way as to obtain oyster flesh extracts having a solid mattercontent of about 15 to about 45 (W/W)%.

This concentration operation is carried out at an elevated temperature,for instance, in the range of 60° C. to 70° C. or even higher. If areduced-pressure, low-temperature concentration process is used, theconcentration operation can then be done at lower temperatures.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is allowed to stand for a givenperiod of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

In this embodiment, the raw oyster flesh used for the first extractionis again fed back to the extractor with a solution received in it.Unlike the first extraction, the extractor is closed up tight this time,and pressure is applied to the oyster flesh.

What pressure is here applied to the oyster flesh is not critical; apressure of 1 atm or higher, for instance, about 1.1 atm (0.11megapascal) to about 2.5 atm (0.25 megapascal) may be applied. Thepressurization time, too, is not critical; a period of time of about 5minutes to about 60 minutes is preferable.

In this way, the rest of various useful components are efficientlyextracted from the once extracted raw oyster flesh, and they areefficiently dissolved in the aqueous solution in the extractor.

The amount of the extracted extracts is an about 60% larger than thatobtained by double extractions under normal pressure.

Then, the aqueous solution in which another portion of extracts has beenextracted from the raw oyster flesh is concentrated, preferably by thereduced-pressure, low-temperature concentration.

Finally, an alcohol solution is added to the thus concentrated solutionto allow the oyster flesh extracts to settle down, and the precipitatesare dried into dry oyster flesh extracts.

Thus, the present invention can provide a method of extracting andpreparing, with an improved degree of extraction, oyster flesh extractsthat contain taurine, glycogens and proteins, the so-calledplatelet-aggregation inhibition substances containing zinc, vitamins,and other helpful substances at increased rates.

The results of the double extraction are now explained with reference tothe FIG. 1 table.

As shown at No. 6 and No. 7 in FIG. 1, the double-extraction operationwas carried out, which involved the first extraction at normal pressure,i.e., 1 atm (0.1 megapascal) for 80 minutes, and the second extractionusing the raw oyster flesh subjected to the first extraction at anincreased pressure, i.e., 1.5 atm (0.15 megapascal) for 20 minutes.

As a result, the extracts were found to contain 32.7 mg of Zn, 109.5 μgof Se, 5.84 mg of Fe and 4.11 mg of Cu per 100 g.

From 20 kg of raw oysters, 772.2 g of dried matter were obtained whenthe first extraction was carried out at 1 atm for 80 minutes, and 306.6g of dried matter were obtained when the second extraction was performedunder an increased pressure of 1.5 atm for 40 minutes, 1,078.8 g in all.

Further, after the extraction at normal pressure, i.e., at 1 atm for 80minutes, the raw oyster flesh subjected to the first extraction wassubjected to another extraction at an increased pressure, i.e., at 1.5atm (0.15 megapascal) for 40 minutes.

Consequently, 100 g of extracts were found to contain 20.9 mg of Zn,127.3 μg of Se, 4.34 mg of Fe and 4.34 mg of Cu, and from 20 kg of rawoysters, 772.2 g of dried matter were obtained at the first extractionat 1 atm for 80 minutes, and 416.5 g were obtained at the secondextraction at an increased pressure, 1,188.7 g in all.

(2) Reduced-Pressure Extraction of Oyster Flesh Extracts

The reduced-pressure extraction is now explained.

First, an extractor was closed up tight and placed under a reducedpressure. Although to what degree the pressure of the extractor isreduced down is not critical; however, the extractor is brought down toa pressure of 1 atm or lower, for instance, about 0.01 atm (0.001megapascal) to about 0.99 atm (0.099 megapascal), although a pressure ofabout 0.1 atm (0.01 megapascal) to about 0.2 atm (0.02 megapascal) isparticularly preferred. How long the pressure is reduced down is notcritical; however, a period of time of about 30 minutes to about 70minutes is applied.

In this way, various effective components are efficiently extracted fromraw oyster flesh, and they are efficiently dissolved in an aqueoussolution in the extractor. In particular, vitamins vulnerable todenaturation and damage or their effective components are extractedintact.

In addition, the amount of the extracts obtained is found to be farlarger than that obtained by extraction at an ordinary pressure of 1 atm(0.1 megapascal).

Then, the aqueous solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

How to concentrate the aqueous solution is not critical; concentrationmay be carried out in such a way as to enable the extracted oyster fleshextracts to have a solid matter content of, for instance, about 15 toabout 45 (W/W)%.

Concentration operation may ordinarily be carried out at an elevatedtemperature, for instance, in the range of 60° C. to 70° C. or evenhigher. If the reduced-pressure, low-temperature concentration processis used, the concentration operation can then be done at lowertemperatures.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is allowed to stand for a givenperiod of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

Thus, the instant embodiment of the invention can provide a method ofextracting and preparing, with an improved degree of extraction, oysterflesh extracts that contain taurin, glycogens, proteins, the so-calledplatelet-aggregation inhibition substances containing zinc, and otherhelpful substances at increased rates. In particular, vitamins andproteins are smoothly extracted intact.

The invention is now explained with reference to FIG. 2 that is a table.

As shown at No. 1 in FIG. 2, with a conventional normal-pressureextraction, that is, when extraction operation was carried out at 1 atmfor 80 minutes, 24.4 mg of Zn, 125.4 μg of Se and 4.22 mg of Fe wereextracted per 100 g, and from 20 kg of shucked raw oysters, there wereobtained 772.2 g of dried matter providing oyster flesh extracts.

On the other hand, with the reduced-pressure extraction, that is, whenextraction operation was done under a reduced pressure of 0.1 atm (0.01megapascal) to 0.2 atm (0.02 megapascal) for 60 minutes, 22.1 mg of Zn,136 μg of Se and 4.8 mg of Fe were extracted per 100 g, and from 20 kgof raw oysters, 1,187 g of dried matter were obtained. Thus, much moreextracts were obtained by the reduced-pressure extraction at 0.1 atm(0.01 megapascal) to 0.2 atm (0.02 megapascal).

When the reduced-pressure extraction was carried out for a varyingextraction time, that is, when the extraction was performed at 0.1 atm(0.01 megapascal) to 0.2 atm (0.02 megapascal) for 53 minutes, 24.7 mgof Zn, 137 μg of Se and 5.08 mg of Fe were extracted per 100 g, and from20 kg of raw oysters, 1,195 g of dried matter were obtained.

The double-extraction process is now explained.

First, oyster flesh extracts are extracted from raw oyster flesh in theso-called normal pressure state, i.e., at 1 atm in the same extractor asalready mentioned.

This extraction, referred to as normal-pressure extraction, is carriedout for a period of time of, for instance, 80 minutes to 120 minutes.

The temperature of the solution is not critical; a temperature of about50° C. to 80° C. is usually preferred, although temperature of lowerthan 50° C. or higher than 80° C. could be used.

The raw oyster flesh extracts extracted at the normal pressure are fedback into the aqueous solution in the extractor to obtain an aqueoussolution in which they are dissolved.

Then, that aqueous solution is concentrated. How to concentrate theaqueous solution is not critical; concentration may be carried out insuch a way as to obtain oyster flesh extracts having a solid mattercontent of about 15 to about 45 (W/W)%.

This concentration operation is carried out at an elevated temperature,for instance, in the range of 60° C. to 70° C. or even higher. If thereduced-pressure, low-temperature concentration process is used, theconcentration operation can then be done at lower temperatures, asalready mentioned.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is allowed to stand for a givenperiod of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

In the instant embodiment, the raw oyster flesh used for the firstextraction is again fed back into the extractor with a solution receivedin it. Unlike the first extraction, the extractor is closed up tight andplaced under a reduced pressure this time.

Although to what degree the pressure of the extractor is reduced down isnot critical; however, the extractor is brought down to a pressure of 1atm or lower, for instance, about 0.01 atm (0.001 megapascal) to about0.99 atm (0.099 megapascal), although a pressure of about 0.1 atm (0.01megapascal) to about 0.2 atm (0.02 megapascal) is particularlypreferred. How long the pressure is reduced down is not critical;however, a period of time of about 30 minutes to about 70 minutes isapplied.

In this way, the rest of various effective components are efficientlyextracted out of the once extracted raw oyster flesh, and they areefficiently dissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is much larger than that obtained byordinary normal-pressure extraction.

Then, the aqueous solution in which another portion of extracts has beenextracted from the raw oyster flesh is concentrated, preferably by thereduced-pressure, low-temperature concentration process.

Finally, an alcohol solution is added to the thus concentrated solutionto allow the oyster flesh extracts to settle down, and the precipitatesare dried into dry oyster flesh extracts.

Even with the double-extraction, it is thus possible to extract andprepare oyster flesh extracts with an improved degree of extraction,which contain larger amounts of taurine, glycogens and proteins, theso-called platelet-aggregation inhibition substances such as zinc, andother useful substances. In particular, vitamins and proteins can beextracted intact.

(3) Selective Extraction Process Enabling Oyster Flesh Extracts to beExtracted by Either Pressure Extraction or Reduced-Pressure Extraction

How to carry out the so-called selective extraction process toselectively increase or decrease the internal pressure of the extractoris now explained.

This selective extraction process is usually carried out with referenceto data in a computer.

In consideration of the merits of the pressure extraction and the meritsof the reduced-pressure extraction, the extraction considered mostpreferred or desired at the time of extraction is selected.

The differences in principle between the pressure extraction and thereduced-pressure extraction are now explained.

The pressure extraction harnesses a phenomenon where, uponpressurization, oyster flesh components move around vigorously in oysterflesh cells so that they run out of the cells through their membranes,resulting in dissolution in an aqueous solution. Therefore, the pressureextraction works for the extraction of components at deep sites of theoyster flesh cells, for instance, components in mitochondria.

With the reduced-pressure extraction, on the other hand, the externalpressure of oyster flesh cells becomes lower than the internal pressure,so that components are sucked out of the cells for extraction anddissolution.

Therefore, the reduced-pressure extraction works especially for theextraction of components at or near the surfaces of the oyster fleshcells.

Another merit of the pressure extraction is that more oyster fleshextracts can be obtained within a shorter period of time. The pressureextraction is also favorable for the extraction of more trace elementshighly stable to pressurization, for instance, zinc or Zn, selenium orSe, iron or Fe, etc.

On the contrary, the reduced-pressure extraction makes use of asituation under a reduced pressure, where there is no or littletemperature rise due to a decreased boiling point.

In other words, the reduced-pressure extraction works for the extractionof nutrient components relatively susceptible of denaturation as byheating such as vitamins and proteins, and especially trace vitaminelements found on cell surfaces.

Further, whether the pressure extraction or the reduced-pressureextraction is preferred for the extraction of oyster flesh extracts isdetermined, for instance, in consideration of data on the state (thickor thin), weight and so on of raw oyster flesh.

Reference is now made to the case where the pressure extraction isselected in the selective extraction step.

First of all, the extractor is closed up tight, and pressurized.

By way of example but not by way of limitation, a pressure of 1 atm orhigher is applied for pressurization, although a pressure of about 1.1atm to about 2.5 atm is preferred. How long the extractor is pressurizedis also not critical, although a pressurization time of about 5 minutesto about 60 minutes is preferred. The temperature is then held at 75° C.to 120° C., and pressurization is accompanied by temperature rises.

During the extraction, it is not necessary to carry out stirring in sucha way as to do no damage to the shucked oyster flesh in the extractor,because efficient extraction is achievable without recourse to agitationaccording to the invention. Stirring may possibly do damage to theeffective components to be extracted.

In this way, various effective components are efficiently extracted fromraw oyster flesh. They are then efficiently dissolved in an aqueoussolution in the extractor.

The amount of the extracts obtained is found to be much more increasedthan that extracted under normal pressure. The extraction time, too, isfound to be far shorter than that applied in conventional manners, andeven so, the same amount of extracts is obtainable.

Then, the solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

How to concentrate the aqueous solution is not critical; concentrationmay be carried out in such a way as to enable the oyster flesh extractsto have a solid matter content of, for instance, about 15 to about 45(W/W)%.

Concentration operation may ordinarily be carried out at an elevatedtemperature, for instance, in the range of 60° C. to 70° C. or evenhigher. If a reduced-pressure, low-temperature heating concentrationprocess is used, the concentration operation can then be done at lowertemperatures.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is typically stirred and allowedto stand for a given period of time until the oyster flesh extractssettle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

Thus, the present invention can provide a method of extracting andpreparing, with an improved degree of extraction, oyster flesh extractsthat contain the so-called platelet-aggregation inhibition substancescontaining taurine, glycogens, proteins, zinc, vitamins, and otherhelpful substances at increased rates.

The double-extraction process is now explained.

First, oyster flesh extracts are extracted from raw oyster flesh in theso-called normal pressure state, i.e., at 1 atm in the same extractor asalready mentioned.

This extraction, referred to as normal-pressure extraction, is carriedout for a period of time of, for instance, 80 minutes to 120 minutes.

The temperature of the solution is not critical; a temperature of about50° C. to 80° C. is usually preferred, although temperature of lowerthan 50° C. or higher than 80° C. could be used.

The raw oyster flesh extracts extracted at the normal pressure are fedback into the aqueous solution in the extractor to obtain an aqueoussolution in which they are dissolved.

Then, that aqueous solution is concentrated. How to concentrate theaqueous solution is not critical; concentration may be carried out insuch a way as to obtain oyster flesh extracts having a solid mattercontent of about 15 to about 45 (W/W)%.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is let stand for a given periodof time until oyster flesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

In this embodiment, the raw oyster flesh subjected to the aforesaidextraction is again placed in the extractor with a solution storedtherein. Unlike the former case, the extractor is closed up tight andpressurized this time.

To what degree the extractor is pressurized is not critical, although apressure of 1 atm or higher, for instance, a pressure of about 1.1 atmto about 2.5 atm is preferably applied. The pressurization time is notcritical, too, although a time of about 5 minutes to about 60 minutes isapplied.

Thus, the rest of various effective components is extracted from the rawoyster flesh that has once been subjected to extraction, and they areefficiently dissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is found to be an about 60% largerthan that obtained by the double-extraction process under normalpressure.

Then, the aqueous solution in which another portion of the oyster fleshextracts is extracted from the raw oyster flesh is concentrated, againpreferably by the reduced-pressure, low-temperature heatingconcentration.

Then, an alcohol solution is added to the obtained concentrated solutionto precipitate out the oyster flesh extracts, and they are dried intodried oyster flesh extracts.

Thus, the present invention can provide a method of extracting andpreparing, with an improved degree of extraction, oyster flesh extractsthat contain taurine, glycogens, proteins, the so-calledplatelet-aggregation inhibition substances such as zinc, vitamins, andother helpful substances at increased rates.

Reference is now made to the case where the reduced-pressure extractionis chosen.

When the reduced-pressure extraction is chosen, for instance, there isno or little temperature rise because of a decreased boiling pointtypically in a reduced-pressure state.

The reduced-pressure extraction works for the extraction of more traceelements relatively susceptible to denaturation as by heating, forinstance, vitamins and proteins.

To what degree the pressure is reduced down is not critical; a pressureof 1 atm or lower is applied, although, by way of example, a pressure ofabout 0.01 atm to about 0.99 atm, especially about 0.1 atm or about 0.2atm is preferred. How long the pressure is brought down, too, is notcritical, although a period of time of about 30 minutes to about 70minutes is applied.

In this way, various effective components are efficiently extracted outof raw oyster flesh, and they are efficiently dissolved in the aqueoussolution in the extractor. Especially easy-to-denature or easy-to-damagevitamins and proteins are extracted or their effective components areextracted intact.

In addition, the amount of the extracts obtained is found to be muchlarger than that obtained by ordinary extraction at normal pressure of 1atm.

Then, the aqueous solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

How to concentrate the aqueous solution is not critical; that is, theaqueous solution may be concentrated in such a way as to allow theoyster flesh extracts to have a solid matter content of, for instance,about 15 to about 45 (W/W)%.

An alcohol solution is added to the solution concentrated to the givenconcentration, and let stand for a given period of time until the oysterflesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

Thus, the present invention can provide a method of extracting andpreparing, with an improved degree of extraction, oyster flesh extractsthat contain taurine, glycogens, proteins, the so-calledplatelet-aggregation inhibition substances such as zinc, vitamins, andother helpful substances at increased rates. In particular, theinvention enables vitamins and proteins to be smoothly extracted intact.

The double-extraction process is now explained.

First, oyster flesh extracts are extracted from raw oyster flesh in theso-called normal pressure state, i.e., at 1 atm in the same extractor asalready mentioned.

This extraction, referred to as normal-pressure extraction, is carriedout for a period of time of, for instance, 80 minutes to 120 minutes.

The temperature of the solution is not critical; a temperature of about50° C. to 80° C. is usually preferred, although temperature of lowerthan 50° C. or higher than 80° C. could be used.

The raw oyster flesh extracts extracted at the normal pressure are fedback into the aqueous solution in the extractor to obtain an aqueoussolution in which they are dissolved.

Then, that aqueous solution is concentrated. How to concentrate theaqueous solution is not critical; concentration may be carried out insuch a way as to obtain oyster flesh extracts having a solid mattercontent of about 15 to about 45 (W/W)%.

An alcohol solution is added to the solution concentrated to the givenconcentration, and the ensuing solution is typically stirred and allowedto stand for a given period of time until the oyster flesh extractssettle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

In the instant embodiment, the raw oyster flesh used for the firstextraction is again fed back into the extractor with the solutionreceived in it. Unlike the first extraction, the extractor is closed uptight and placed under a reduced pressure this time.

Although to what degree the pressure of the extractor is reduced down isnot critical; however, the extractor is brought down to a pressure of 1atm or lower, for instance, about 0.001 atm to about 0.99 atm, althougha pressure of about 0.1 atm to about 0.2 atm is particularly preferred.How long the pressure is reduced down is not critical; however, a periodof time of about 30 minutes to about 70 minutes is applied.

In this way, the rest of various effective components are efficientlyextracted out of the once extracted raw oyster flesh from, and they areefficiently dissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is much larger than that obtained byan ordinary single extraction operation under normal pressure.

Then, the aqueous solution in which another portion of extracts has beenextracted from the raw oyster flesh is concentrated, preferably byheating concentration at low temperature under reduced pressure.

Finally, an alcohol solution is added to the thus concentrated solutionto allow the oyster flesh extracts to settle down, and the precipitatesare dried into dry oyster flesh extracts.

Thus, the instant embodiment of the invention can provide adouble-extraction method of extracting and preparing, with an improveddegree of extraction, oyster flesh extracts that contain taurine,glycogens, proteins, the so-called platelet-aggregation inhibitionsubstances such as zinc, and other helpful substances at increasedrates. In particular, vitamins and proteins are smoothly extractedintact.

(4) Application of the Reduced-Pressure, Low-Temperature HeatingConcentration to the Concentration Step

(a) Pressure Extraction Using the Reduced-Pressure, Low-TempertureHeating Concentration Process

Reference is now made to one preferable embodiment of the pressureextraction of extracting oyster flesh extracts in an extractor that isclosed up tight and pressurized, wherein the reduced-pressure,low-temperature heating concentration process is applied to theconcentration step.

By way of example but not by way of limitation, a pressure of 1 atm (0.1megapascal) or higher is applied for pressurization, although a pressureof about 1.1 atm to about 2.5 atm is preferred. How long the extractoris pressurized is also not critical, although a pressurization time ofabout 5 minutes to about 60 minutes is preferred. The temperature isthen held at 75° C. to 120° C., and pressurization is accompanied bytemperature rises.

During the extraction, it is not necessary to carry out stirring in sucha way as to do no damage to the shucked oyster flesh in the extractor,because efficient extraction is achievable without recourse to agitationaccording to the invention.

In this way, various effective components are efficiently extracted fromraw oyster flesh. They are then efficiently dissolved in an aqueoussolution in the extractor.

The amount of the extracts obtained is found to be much more increasedthan that extracted under normal pressure. The extraction time, too, isfound to be far shorter than that applied in conventional manners.

Then, the solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

Here, the aqueous solution is concentrated by reduced-pressure,low-temperature heating concentration process in such a way as to obtainoyster flesh extracts having a dry matter content of, for instance,about 15 to about 45 (W/W)%.

Concentration operation may ordinarily be carried out at an elevatedtemperature, for instance, in the range of 60° C. to 70° C. or evenhigher. If the reduced-pressure, low-temperature heating concentrationprocess is used, the concentration operation can then be done at lowertemperatures (60° C. or lower).

It has now been found that the reduced-pressure, low-temperature heatingconcentration, i.e., the concentration operation by heating at lowtemperature is an all-important factor for the extraction of oysterflesh extracts.

It has already been found that as a solution of proteins that are oysterflesh extracts is held in a high-temperature state, it causes them tocondense hard; however, in a low-temperature state, they condensegently. As the gently condensing proteins exist in the solution, theirarea of contact with the solution becomes large.

For instance, it is understood that low-temperature pasteurized milk isbetter in digestibility than high-temperature one, because the area ofcontact with digestive fluid of proteins in the low-temperaturepasteurized milk is larger than that of proteins in the high-temperatureone.

The proteins denature and settle down by contact with an alcoholsolution, as described with reference to the next precipitation step. Atthis time, the gently condensing proteins are larger in the area ofcontact with the alcohol solution than the proteins condensed hard.Thus, the gently condensing proteins are likely to denature and settledown.

Thus, the reduced-pressure, low-temperature heating concentrationensures gentle condensation of proteins extracted from raw oysters,whereby the area of contact of the proteins with the alcohol is largerthan that of proteins condensed at high temperatures, resulting inprecipitation of a lot more proteins, from which a lot more dry mattercan be obtained.

Thus, an alcohol solution is added to the solution concentrated to thegiven concentration, after which the ensuing solution is stirred.

After stirring, the solution is separated into a supernatant portion anda precipitate portion at a ratio of 0.5 to 2.5:95 to 7.5.

With a conventional concentration process, a concentration solution isseparated into a supernatant portion and a precipitate portion at aratio of only about 5.8 to about 4.2; the proportion of the supernatantportion is relatively high. As a result, the amount of dry matterobtained by drying the precipitates becomes relatively small. With thereduced-pressure, low-temperature heating concentration used herein,however, there is a significant increase in the amount of dry matter.

Thus, the precipitates obtained in larger amounts relative to thesupernatant are dried into dry oyster flesh extracts.

FIG. 3 is illustrative of the contents of trace elements in 100 g of dryoyster flesh extracts in the case of normal-pressure (1 atm) heatingconcentration, and in the case of reduced-pressure (0.1 atm) heatingconcentration. To make clear differences between the results, oysterflesh extracts were extracted from raw oyster flesh in a conventionalextraction process, and oyster flesh extracts obtained by heating in anormal-pressure (1 atm) state were used.

As can be seen from FIG. 3, 26.0 mg of zinc or Ze, 78 μg of selenium orSe and 2.38 g of extracts are contained per 100 g in the case ofnormal-pressure heating concentration, whereas the elements and extractsare contained in more increased amounts per 100 g in the case of thereduced-pressure heating concentration: 31.4 mg of zinc or Ze, 101 μg ofselenium or Se and 2.64 g of extracts.

These results show that as the alcohol solution is added to theconcentrated solution obtained in the normal-pressure thermalconcentration process, it allows essential trace elements such as zinc(Ze) and selenium (Se) present ordinarily in the supernatant to beprecipitated and collected (together with gently denatured proteins).

In other words, it has been found that with the reduced-pressure,low-temperature heating concentration, the effective components in theconcentrated solution can be efficiently passed into the precipitateportion without being left in the supernatant portion.

With the reduced-pressure, low-temperature heating concentration, it isthus possible to achieve a method of preparing oyster flesh extracts byextraction, concentration, precipitation and collection, which enablestrace elements containing various effective components such as zinc (Ze)and selenium (Se) to be contained therein with high contents and a highdegree of extraction. The advantage could be much more enhanced by acombination of pressure extraction and reduced-pressure, low-temperatureheating concentration.

The double-extraction process using the reduced-pressure,low-temperature concentration process is now explained.

In the double-extraction process, too, the content and the degree ofextraction of zinc (Ze) and selenium (Se) could be much more improved ifthe reduced-pressure, low-temperature heating concentration is appliedto its concentration step.

First of all, oyster flesh extracts are extracted from raw oyster fleshin an extractor in the so-called normal-pressure or 1 atm state.

This extraction, referred to as the normal-pressure extraction, iscarried out for, e.g., 80 minutes to 120 minutes.

Here, the temperature of the solution used is not critical; atemperature of about 50° C. to about 80° C. is usually applied, althoughtemperature of lower than 50° C. or higher than 80° C. could be used.

Then, the raw oyster flesh extracts extracted at the normal pressure arefed into a solution in the extractor, in which they are dissolved,giving an aqueous solution.

Then, that aqueous solution is concentrated.

To this end, the aforesaid reduced-pressure, low-temperature heatingconcentration is carried out in such a way as to give oyster fleshextracts having a solid matter content of about 15 to about 45 (W/W)%.

An alcohol solution is then added to the solution concentrated to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until oyster flesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

In this embodiment, the once extracted raw oyster flesh is again placedin the extractor with a solution stored therein. Unlike the former case,the extractor is closed up tight and pressurized this time.

To what degree the extractor is pressurized is not critical, although apressure of 1 atm or higher, for instance, a pressure of about 1.1 atmto about 2.5 atm is preferably applied. The pressurization time is notcritical, too, although a time of about 5 minutes to about 60 minutes isapplied.

Thus, the rest of various effective components are efficiently extractedfrom the once extracted raw oyster flesh, and they are efficientlydissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is found to be an about 60% largerthan that obtained by the double-extraction process under normalpressure.

Then, the aqueous solution in which another portion of oyster fleshextracts are extracted from the raw oyster flesh is concentrated, againby the reduced-pressure, low-temperature heating concentration.

Then, an alcohol solution is added to the obtained concentrated solutionto precipitate out the oyster flesh extracts, and they are dried intodried oyster flesh extracts.

(b) Reduced-Pressure Extraction Using the Reduced-Pressure,Low-Temperature Heating Concentration

Reference is now made to one preferable embodiment of thereduced-pressure extraction of oyster flesh extracts in an extractorclosed up tight and put under reduced pressure, to which thereduced-pressure, low-temperature heating concentration process isapplied.

First of all, the extractor is closed up tight and put under a reducedpressure.

Although to what degree the pressure of the extractor is reduced down isnot critical; however, the extractor is brought down to a pressure of 1atm or lower, for instance, about 0.01 atm to about 0.99 atm, although apressure of about 0.1 atm to about 0.2 atm is particularly preferred.How long the pressure is reduced down is again not critical; however, aperiod of time of about 30 minutes to about 70 minutes is applied.

In this way, various effective components are efficiently extracted outof the raw oyster flesh, and they are efficiently dissolved in theaqueous solution in the extractor. In particular, vitamins and proteinsvulnerable to denaturation and damage or their effective components canbe extracted intact.

In addition, the amount of the extracts obtained is found to be muchlarger than that obtained by a conventional normal-pressure or 1 atmextraction.

Then, the aqueous solution in which the oyster flesh extracts beenextracted from the raw oyster flesh is concentrated.

Here, the aforesaid reduced-pressure, low-temperature heatingconcentration process is applied to the concentration of the aqueoussolution in such a way as to obtain oyster flesh extracts having a solidmatter content of, for instance, about 15 to about 45 (W/W)%.

The reduced-pressure, low-temperature heating concentration, i.e., theconcentration operation by heating at low temperature is anall-important factor for the extraction of oyster flesh extracts, aspreviously noted.

It has already been found that as a solution of proteins that are oysterflesh extracts is held in a high-temperature state, it causes them tocondense hard; however, in a low-temperature state, they condensegently. As the gently condensing proteins exist in the solution, theirarea of contact with the solution becomes large.

For instance, it is understood that low-temperature pasteurized milk isbetter in digestibility than high-temperature one, because the area ofcontact with digestive fluid of proteins in the low-temperaturepasteurized milk is larger than that of proteins in the high-temperatureone.

The proteins denature and settle down by contact with an alcoholsolution. In this case, the gently condensing proteins are larger in thearea of contact with the alcohol solution than the proteins condensedhard. Thus, the gently condensing proteins are likely to denature andsettle down.

Thus, the reduced-pressure, low-temperature heating concentrationensures gentle condensation of proteins extracted from raw oysters,whereby the area of contact of the proteins with the alcohol is largerthan that of proteins condensed at high temperatures, resulting inprecipitation of a lot more proteins, from which a lot more dry mattercan be obtained. In addition, increased amounts of effective componentssuch as zinc and selenium can be obtained together with theprecipitates.

Then, the alcohol solution is added to the solution concentrated to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

Reference is now made to the double-extraction using thereduced-pressure, low-temperature heating concentration process.

First of all, oyster flesh extracts are extracted from raw oyster fleshin an extractor in the so-called normal-pressure or 1 atm state.

This extraction, referred to as the normal-pressure extraction, iscarried out for a period of time, e.g., 80 minutes to 120 minutes.

Here, the temperature of the solution used is not critical; atemperature of about 50° C. to about 80° C. is usually applied, althoughtemperature of lower than 50° 0.0C or higher than 80° C. could be used.

Then, the raw oyster flesh extracts extracted at the normal pressure arefed into a solution in the extractor, in which they are dissolved,giving an aqueous solution.

Then, that aqueous solution is concentrated. To this end, the aforesaidreduced-pressure, low-temperature heating concentration is carried outin such a way as to give oyster flesh extracts having a solid mattercontent of about 15 to about 45 (W/W)%.

An alcohol solution is then added to the solution concentrated to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until the oyster flesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

In this embodiment, the once extracted raw oyster flesh is again placedin an extractor with a solution stored therein. Unlike the former case,the extractor is closed up tight and put under a reduced pressure thistime.

To what degree the pressure of the extractor is reduced down is notcritical, although a pressure of 1 atm or lower, for instance, apressure of about 0.001 atm to about 0.99 atm, and especially about 0.1atm to about 0.2 atm is preferably applied. How long the reducedpressure is applied is not critical, too, although a time of about 30minutes to about 70 minutes is applied.

Thus, the rest of various effective components are efficiently extractedfrom the raw oyster flesh that has once been subjected to extraction,and they are efficiently dissolved in the aqueous solution in theextractor.

The amount of the extracts obtained is found to be much larger than thatextracted under normal pressure.

Then, the aqueous solution in which another portion of oyster fleshextracts are extracted from the raw oyster flesh is concentrated, againby the reduced-pressure, low-temperature heating concentration.

Then, an alcohol solution is added to the obtained concentrated solutionto precipitate out the oyster flesh extracts, and they are dried intodried oyster flesh extracts.

Even with the double-extraction, it is thus possible to extract andprepare oyster flesh extracts with an improved degree of extraction,which contain larger amounts of taurine, glycogens and proteins, theso-called platelet-aggregation inhibition substances such as zinc, andother useful substances. In particular, vitamins and proteins can beextracted intact.

(c) Selective Extraction Using the Reduced-Pressure, Low-TemperatureHeating Concnetration Process

Reference is now made of one preferable embodiment of the so-calledselective extraction of increasing or reducing the pressure of theclosed extractor, to which the reduced-pressure, low-temperature heatingconcentration process is applied.

This selective extraction process is usually carried out with referenceto data in a computer.

In consideration of the merits of the pressure extraction and the meritsof the reduced-pressure extraction, the extraction most preferred ordesired at the time of extraction is selected.

One merit of the pressure extraction is that more oyster flesh extractscan be obtained within a shorter period of time. The pressure extractionis also favorable for extraction of more trace elements less susceptibleto denature or damage even upon pressurization or heating, for instance,zinc or Zn, selenium or Se, iron or Fe, etc.

On the contrary, the reduced-pressure extraction makes use of asituation under reduced pressure, where there is no or littletemperature rise.

In other words, the reduced-pressure extraction works for the extractionof trace elements relatively susceptible to denaturation and damage asby heating such as vitamins and proteins, and especially trace vitaminelements found on cell surfaces.

Further, whether the pressure extraction or the reduced-pressureextraction is preferred for the extraction of oyster flesh extracts isdetermined, for instance, in consideration of data on the state, weightand so on of raw oyster flesh.

Reference is now made to the case where the pressure extraction isselected in the selective extraction step. In this case, thereduced-pressure, low-temperature heating concentration process isapplied to the concentration step.

First, the extractor is closed up tight, and pressurized.

By way of illustration but not by way of limitation, a pressure of 1 atmor higher is applied for pressurization, although a pressure of about1.1 atm to about 2.5 atm is preferred. How long the extractor ispressurized is also not critical, although a pressurization time ofabout 5 minutes to about 60 minutes is preferred. The temperature isthen held at 75° C. to 120° C., and pressurization is accompanied bytemperature rises.

During the extraction, it is not necessary to carry out stirring in sucha way as to do no damage to the shucked oyster flesh in the extractor,because efficient extraction is achievable without recourse to agitationaccording to the invention. Stirring may possibly do damage to theeffective components to be extracted.

In this way, various effective components are efficiently extracted fromraw oyster flesh. They are then efficiently dissolved in an aqueoussolution in the extractor.

The amount of the extracts obtained is found to be much more increasedthan that extracted under normal pressure. The extraction time, too, isfound to be far shorter than that applied in conventional manners, andeven so, the same amount of extracts is obtainable.

Then, the solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

Here, the reduced-pressure, low-temperature heating concentrationprocess is applied to the concentration of the solution.

This is carried out in such a way as to enable the extracted oysterflesh extracts to have a solid matter content of, for instance, about 15to 45 (W/W)%.

An alcohol solution is added to the solution concentrated by thereduced-pressure, low-temperature heating concentration process to thegiven concentration, and the ensuing solution is stirred and allowed tostand for a given period of time until the oyster flesh extracts settledown.

Finally, the precipitates are collected, and dried, yielding driedoyster flesh extracts.

Reference is now made to the double-extraction using thereduced-pressure, low-temperature heating concentration process.

First of all, oyster flesh extracts are extracted from raw oyster fleshin an extractor in the so-called normal-pressure or 1 atm state.

This extraction, referred to as the normal-pressure extraction, iscarried out for a period of time, e.g., 80 minutes to 120 minutes.

Here, the temperature of the solution used is not critical; atemperature of about 50° C. to about 80° C. is usually applied, althoughtemperature of lower than 50° C. or higher than 80° C. could be used.

Then, the raw oyster flesh extracts extracted at the normal pressure arefed into a solution in the extractor, in which they are dissolved,giving an aqueous solution.

Then, that aqueous solution is concentrated. To this end, the aforesaidreduced-pressure, low-temperature heating concentration is carried outin such a way as to give oyster flesh extracts having a solid mattercontent of about 15 to 45 (W/W)%.

An alcohol solution is then added to the solution concentrated by thereduced-pressure, low-temperature heating concentration process to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until the oyster flesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

In this embodiment, the raw oyster flesh once subjected to extraction isagain placed in an extractor with a solution stored therein. Unlike theformer case, the extractor is closed up tight and pressurized this time.

To what degree the extractor is pressurized is not critical, although apressure of 1 atm or higher, for instance, a pressure of about 1.1 atmto about 2.5 atm. How long the extractor is pressurized is not critical,too, although a time of about 30 minutes to about 70 minutes is applied.

Thus, various effective components are again efficiently extracted fromthe raw oyster flesh that has once been subjected to extraction, andthey are efficiently dissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is found to be an about 60% largerthan that extracted by double extractions under normal pressure.

Then, the aqueous solution in which another portion of oyster fleshextracts are extracted from the raw oyster flesh is concentrated, againby the reduced-pressure, low-temperature heating concentration.

Then, an alcohol solution is added to the obtained concentrated solutionto precipitate out the oyster flesh extracts, and they are dried intodried oyster flesh extracts.

Reference is now made to the case where the reduced-pressure extractionusing the reduced-pressure, low-temperature heating concentrationprocess is chosen.

When the reduced-pressure extraction is chosen, there is no or littletemperature rise because of a decreased boiling point in areduced-pressure state, as previously noted.

The reduced-pressure extraction works for the extraction of a lot moretrace elements relatively susceptible to denaturation as by heating, forinstance, vitamins or proteins.

Although to what degree the pressure of the extractor is reduced down isnot critical; however, the extractor is brought down to a pressure of 1atm or lower, for instance, about 0.01 atm to about 0.99 atm, although apressure of about 0.1 atm to about 0.2 atm is particularly preferred.How long the pressure is reduced down is again not critical; however, aperiod of time of about 30 minutes to about 70 minutes is applied.

In this way, various effective components are efficiently extracted outof the raw oyster flesh, and they are efficiently dissolved in theaqueous solution in the extractor. In particular, vitamins and proteinsvulnerable to denaturation and damage or their effective components canbe extracted intact.

In addition, the amount of the extracts obtained is found to be muchlarger than that obtained by a conventional normal-pressure or 1 atmextraction.

Then, the aqueous solution in which the oyster flesh extracts have beenextracted from the raw oyster flesh is concentrated.

Here, the aforesaid reduced-pressure, low-temperature heatingconcentration process is applied to the concentration of the aqueoussolution in such a way as to obtain oyster flesh extracts having a solidmatter content of, for instance, about 15 to about 45 (W/W)%.

Then, the alcohol solution is added to the solution concentrated to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until the oyster flesh extracts settle down.

Finally, the precipitates are collected and dried into dry oyster fleshextracts.

Reference is now made to the double-extraction using thereduced-pressure, low-temperature heating concentration process.

First of all, oyster flesh extracts are extracted from raw oyster fleshin an extractor in the so-called normal-pressure or 1 atm state.

This extraction, referred to as the normal-pressure extraction, iscarried out for a period of time, e.g., 80 minutes to 120 minutes.

Here, the temperature of the solution used is not critical; atemperature of about 50° C. to about 80° C. is usually applied, althoughtemperature of lower than 50° C. or higher than 80° C. could be used.

Then, the raw oyster flesh extracts extracted at the normal pressure arefed into a solution in the extractor, in which they are dissolved,giving an aqueous solution.

Then, that aqueous solution is concentrated. To this end, the aforesaidreduced-pressure, low-temperature heating concentration is carried outin such a way as to give oyster flesh extracts having a solid mattercontent of about 15 to 45 (W/W)%.

An alcohol solution is then added to the solution concentrated by thereduced-pressure, low-temperature heating concentration process to thegiven concentration, and the ensuing solution is let stand for a givenperiod of time until the oyster flesh extracts settle down.

The precipitates are collected and dried into dry oyster flesh extracts.

In this embodiment, the raw oyster flesh once subjected to extraction isagain placed in an extractor with a solution stored therein. Unlike theformer case, the extractor is closed up tight and put under a reducedpressure this time.

To what degree the pressure of the extractor is reduced down is notcritical, although a pressure of 1 atm or lower, for instance, apressure of about 0.001 atm to about 0.99 atm, and especially about 0.1atm to about 0.2 atm is preferably applied. How long the reducedpressure is applied is not critical, too, although a time of about 30minutes to about 70 minutes is applied.

Thus, the rest of various effective components are efficiently extractedfrom the once extracted raw oyster flesh, and they are efficientlydissolved in the aqueous solution in the extractor.

The amount of the extracts obtained is found to be much larger than thatextracted by a single extraction under normal pressure.

Then, the aqueous solution in which another portion of oyster fleshextracts are extracted from the raw oyster flesh is concentrated, againby the reduced-pressure, low-temperature heating concentration.

Then, an alcohol solution is added to the obtained concentrated solutionto precipitate out the oyster flesh extracts, and they are dried intodried oyster flesh extracts.

1. A method of preparing oyster flesh extracts, comprising: anextraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and pressurizing saidraw oyster flesh to 1 atm or higher to extract oyster flesh extractsfrom said raw oyster flesh in a pressurized state, and feeding saidoyster flesh extracts into said solution in said extractor, aconcentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein, a precipitation step of adding analcohol solution to a solution concentrated in said concentration stepto precipitate out said oyster flesh extracts, and a formation step ofdrying precipitates obtained in said precipitation step into dry oysterflesh extracts.
 2. A method of preparing oyster flesh extracts,comprising: a first extraction step of placing raw oyster flesh in anextractor with a solution stored therein, and putting said raw oysterflesh in a normal pressure state in said extractor to extract a portionof oyster flesh extracts from said raw oyster flesh, and feeding saidportion of oyster flesh extracts into said extraction solution, a firstconcentration step of concentrating said extraction solution with saidportion of oyster flesh extracts fed therein, a first precipitation stepof adding an alcohol solution to a solution concentrated in said firstconcentration step to precipitate out said portion of oyster fleshextracts, a first formation step of drying precipitates obtained in saidfirst precipitation step into dry oyster flesh extracts, a secondextraction step of again placing said raw oyster flesh used in saidfirst extraction step in an extractor with a solution stored therein,pressurizing said raw oyster flesh to 1 atm or higher in said extractorto extract another portion of oyster flesh extracts from said raw oysterflesh in a pressurized state, and feeding said another portion of oysterflesh extracts in an extraction solution, a second concentration step ofconcentrating said extraction solution with said another portion ofoyster flesh extracts fed therein, a second precipitation step of addingan alcohol solution to a solution concentrated in said secondconcentration step to precipitate out said another portion of oysterflesh extracts, and a second formation step of drying precipitatesobtained in said second precipitation step into dry oyster fleshextracts.
 3. A method of preparing oyster flesh extracts, comprising: anextraction step of placing raw oyster flesh in an extractor with asolution stored therein, closing up said extractor and putting said rawoyster flesh under a reduced pressure of 1 atm or lower to extractoyster flesh extracts from said raw oyster flesh in a reduced-pressurestate, and feeding said oyster flesh extracts into said solution in saidextractor, a concentration step of concentrating an extraction solutionwith said oyster flesh extracts fed therein, a precipitation step ofadding an alcohol solution to a solution concentrated in saidconcentration step to precipitate out said oyster flesh extracts, and aformation step of drying precipitates obtained in said precipitationstep into dry oyster flesh extracts.
 4. A method of preparing oysterflesh extracts, comprising: a first extraction step of placing rawoyster flesh in an extractor with a solution stored therein, and puttingsaid raw oyster flesh in a normal pressure state in said extractor toextract a portion of oyster flesh extracts from said raw oyster flesh,and feeding said portion of oyster flesh extracts into an extractionsolution, a first concentration step of concentrating said extractionsolution with said portion of oyster flesh extracts fed therein, a firstprecipitation step of adding an alcohol solution to a solutionconcentrated in said first concentration step to precipitate out saidportion of oyster flesh extracts, a first formation step of dryingprecipitates obtained in said first precipitation step into dry oysterflesh extracts, a second extraction step of again placing said rawoyster flesh used in said first extraction step in an extractor with asolution stored therein, putting said raw oyster flesh under a reducedpressure of 1 atm or lower in said extractor to extract another portionof oyster flesh extracts from said raw oyster flesh in areduced-pressure state, and feeding said another portion of oyster fleshextracts in said extraction solution, a second concentration step ofconcentrating said extraction solution with said another portion ofoyster flesh extracts fed therein, a second precipitation step of addingan alcohol solution to a solution concentrated in said secondconcentration step to precipitate out said another portion of oysterflesh extracts, and a second formation step of drying precipitatesobtained in said second precipitation step into dry oyster fleshextracts.
 5. A method of preparing oyster flesh extracts, comprising: aselective extraction step of selecting either a pressure extraction stepof placing raw oyster flesh in an extractor with a solution storedtherein, closing up said extractor and pressurizing said raw oysterflesh to 1 atm or higher to extract oyster flesh extracts from said rawoyster flesh in a pressurized state or a reduced-pressure extractionstep of putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state, a feed step of extractingoyster flesh extracts from said raw oyster flesh in either said pressureextraction step or said reduced-pressure extraction step, and feedingsaid oyster flesh extracts into said solution in said extractor, aconcentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein, a precipitation step of adding analcohol solution to a solution concentrated in said concentration stepto precipitate out said oyster flesh extracts, and a formation step ofdrying precipitates obtained in said precipitation step into dry oysterflesh extracts.
 6. A method of preparing oyster flesh extracts,comprising: a first extraction step of placing raw oyster flesh in anextractor with a solution stored therein, and putting said raw oysterflesh in a normal pressure state in said extractor to extract a portionof oyster flesh extracts from said raw oyster flesh, and feeding saidportion of oyster flesh extracts into said extraction solution, a firstconcentration step of concentrating said extraction solution with saidportion of oyster flesh extracts fed therein, a first precipitation stepof adding an alcohol solution to a solution concentrated in said firstconcentration step to precipitate out said portion of oyster fleshextracts, a first formation step of drying precipitates obtained in saidfirst precipitation step into dry oyster flesh extracts, a selectiveextraction step of selecting either a pressure extraction step of againplacing said raw oyster flesh used in said first extraction step in anextractor with a solution stored therein, and pressurizing said rayoyster flesh to 1 atm or higher in said extractor to extract anotherportion of oyster flesh extracts from said raw oyster flesh in apressurized state or a reduced-pressure extraction step of putting saidraw oyster flesh under a reduced pressure of 1 atm or lower in saidextractor to extract another portion of oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state, a second feed step offeeding said another portion of oyster flesh extracts obtained in eithersaid pressure extraction step or said reduced-pressure extraction stepinto an extraction solution, a second concentration step ofconcentration said extraction solution with said another portion ofoyster flesh extracts fed therein, a second precipitation step of addingan alcohol solution to a solution concentrated in said secondconcentration step, and a second formation step of drying precipitatesobtained in said second precipitation step into dry oyster fleshextracts.
 7. A method of preparing oyster flesh extracts, comprising: anextraction step of placing raw oyster flesh in an extractor with asolution stored therein, extracting oyster flesh extracts from said rawoyster flesh in said extractor, and feeding said oyster flesh extractsinto said solution in said extractor, a concentration step ofconcentrating an extraction solution with said oyster flesh extracts fedtherein, a precipitation step of adding an alcohol solution to asolution concentrated in said concentration step to precipitate out saidoyster flesh extracts, and a formation step of drying precipitatesobtained in said precipitation step into dry oyster flesh extracts,wherein: in said concentration step, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and in saidprecipitation step, said alcohol solution is added to said concentratedsolution in said concentration step, and the resultant solution isstirred and let stand for separation into a supernatant liquid portionand a precipitate portion at a ratio of 0.5:9.5 to 2.5:7.5.
 8. A methodof preparing oyster flesh extracts, comprising: an extraction step ofplacing raw oyster flesh in an extractor with a solution stored therein,closing up said extractor and pressurizing said raw oyster flesh to 1atm or higher to extract oyster flesh extracts from said raw oysterflesh in a pressurized state, and feeding said oyster flesh extractsinto said solution in said extractor, a concentration step ofconcentrating an extraction solution with said oyster flesh extracts fedtherein, a precipitation step of adding an alcohol solution to asolution concentrated in said concentration step to precipitate out saidoyster flesh extracts, and a formation step of drying precipitatesobtained in said precipitation step into dry oyster flesh extracts,wherein: in said concentration step, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and in saidprecipitation step, said alcohol solution is added to said concentratedsolution in said concentration step, and the resultant solution isstirred and let stand for separation into a supernatant liquid portionand a precipitate portion at a ratio of 0.5:9.5 to 2.5:7.5.
 9. A methodof preparing oyster flesh extracts, comprising: a first extraction stepof placing raw oyster flesh in an extractor with a solution storedtherein, and putting said raw oyster flesh in a normal pressure state insaid extractor to extract a portion of oyster flesh extracts from saidraw oyster flesh, and feeding said portion of oyster flesh extracts intosaid extraction solution, a first concentration step of concentratingsaid extraction solution with said portion of oyster flesh extracts fedtherein, a first precipitation step of adding an alcohol solution to asolution concentrated in said first concentration step to precipitateout said portion of oyster flesh extracts, a first formation step ofdrying precipitates obtained in said first precipitation step into dryoyster flesh extracts, a second extraction step of again placing saidraw oyster flesh used in said first extraction step in an extractor witha solution stored therein, pressurizing said raw oyster flesh to apressure of 1 atm or higher in said extractor to extract another portionof oyster flesh extracts from said raw oyster flesh in a pressurizedstate, and feeding said another portion of oyster flesh extracts in saidextraction solution, a second concentration step of concentrating anextraction solution with said another portion of oyster flesh extractsfed therein, a second precipitation step of adding an alcohol solutionto a solution concentrated in said second concentration step toprecipitate out said another portion of oyster flesh extracts, and asecond formation step of drying precipitates obtained in said secondprecipitation step into dry oyster flesh extracts, wherein: in each ofsaid concentration steps, said extraction solution is put under areduced pressure of 1 atm or lower and concentrated by low-temperatureheating in a reduced-pressure state, and in each of said precipitationsteps, said alcohol solution is added to said concentrated solution insaid concentration step, and the resultant solution is stirred and letstand for separation into a supernatant liquid portion and a precipitateportion at a ratio of 0.5:9.5 to 2.5:7.5.
 10. A method of preparingoyster flesh extracts, comprising: an extraction step of placing rawoyster flesh in an extractor with a solution stored therein, closing upsaid extractor and putting said ray oyster flesh under a reducedpressure of 1 atm or lower to extract oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state, and feeding said oysterflesh extracts into said solution in said extractor, a concentrationstep of concentrating an extraction solution with said oyster fleshextracts fed therein, a precipitation step of adding an alcohol solutionto a solution concentrated in said concentration step to precipitate outsaid oyster flesh extracts, and a formation step of drying precipitatesobtained in said precipitation step into dry oyster flesh extracts,wherein: in said concentration step, said extraction solution is putunder a reduced pressure of 1 atm or lower and concentrated bylow-temperature heating in a reduced-pressure state, and in saidprecipitation step, said alcohol solution is added to said concentratedsolution in said concentration step, and the resultant solution isstirred and let stand for separation into a supernatant liquid portionand a precipitate portion at a ratio of 0.5:9.5 to 2.5:7.5.
 11. A methodof preparing oyster flesh extracts, comprising: a first extraction stepof placing raw oyster flesh in an extractor with a solution storedtherein, and putting said raw oyster flesh in a normal pressure state insaid extractor to extract a portion of oyster flesh extracts from saidraw oyster flesh, and feeding said portion of oyster flesh extracts intoan extraction solution, a first concentration step of concentrating saidextraction solution with said portion of oyster flesh extracts fedtherein, a first precipitation step of adding an alcohol solution to asolution concentrated in said first concentration step to precipitateout said portion of oyster flesh extracts, a first formation step ofdrying precipitates obtained in said first precipitation step into dryoyster flesh extracts, a second extraction step of again placing saidraw oyster flesh used in said first extraction step in an extractor witha solution stored therein, putting said raw oyster flesh under a reducedpressure of 1 atm or lower in said extractor to extract another portionof oyster flesh extracts from said raw oyster flesh in areduced-pressure state, and feeding said another portion of oyster fleshextracts in said extraction solution, a second concentration step ofconcentrating said extraction solution with said another portion ofoyster flesh extracts fed therein, a second precipitation step of addingan alcohol solution to a solution concentrated in said secondconcentration step to precipitate out said another portion of oysterflesh extracts, and a second formation step of drying precipitatesobtained in said second precipitation step into dry oyster fleshextracts, wherein: in each of said concentration steps, said extractionsolution is put under a reduced pressure of 1 atm or lower andconcentrated by low-temperature heating in a reduced-pressure state, andin each of said precipitation steps, said alcohol solution is added tosaid concentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.
 12. A method of preparing oyster flesh extracts, comprising: aselective extraction step of selecting either a pressure extraction stepof placing raw oyster flesh in an extractor with a solution storedtherein, closing up said extractor and pressurizing said raw oysterflesh to 1 atm or higher to extract oyster flesh extracts from said rawoyster flesh in a pressurized state or a reduced-pressure extractionstep of putting said raw oyster flesh under a reduced pressure of 1 atmor lower in said extractor to extract oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state, a feed step of extractingoyster flesh extracts from said raw oyster flesh in either said pressureextraction step or said reduced-pressure extraction step, and feedingsaid oyster flesh extracts into said solution in said extractor, aconcentration step of concentrating an extraction solution with saidoyster flesh extracts fed therein, a precipitation step of adding analcohol solution to a solution concentrated in said concentration stepto precipitate out said oyster flesh extracts, and a formation step ofdrying precipitates obtained in said precipitation step into dry oysterflesh extracts, wherein: in said concentration step, said extractionsolution is put under a reduced pressure of 1 atm or lower andconcentrated by low-temperature heating in a reduced-pressure state, andin said precipitation step, said alcohol solution is added to saidconcentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.
 13. A method of preparing oyster flesh extracts, comprising: afirst extraction step of placing raw oyster flesh in an extractor with asolution stored therein, and putting said raw oyster flesh in a normalpressure state in said extractor to extract a portion of oyster fleshextracts from said raw oyster flesh, and feeding said portion of oysterflesh extracts into said extraction solution, a first concentration stepof concentrating said extraction solution with said portion of oysterflesh extracts fed therein, a first precipitation step of adding analcohol solution to a solution concentrated in said first concentrationstep to precipitate out said portion of oyster flesh extracts, a firstformation step of drying precipitates obtained in said firstprecipitation step into dry oyster flesh extracts, a selectiveextraction step of selecting either a pressure extraction step of againplacing said raw oyster flesh used in said first extraction step in anextractor with a solution stored therein, and pressurizing said rawoyster flesh to 1 atm or higher in said extractor to extract anotherportion of oyster flesh extracts from said raw oyster flesh in apressurized state or a reduced-pressure extraction step of putting saidray oyster flesh under a reduced pressure of 1 atm or lower in saidextractor to extract another portion of oyster flesh extracts from saidraw oyster flesh in a reduced-pressure state, a second feed step offeeding said another portion of oyster flesh extracts obtained in eithersaid pressure extraction step or said reduced-pressure extraction stepinto an extraction solution, a second concentration step ofconcentration said extraction solution with said another portion ofoyster flesh extracts fed therein, a second precipitation step of addingan alcohol solution to a solution concentrated in said secondconcentration step, and a second formation step of drying precipitatesobtained in said second precipitation step into dry oyster fleshextracts, wherein: in each of said concentration steps, said extractionsolution is put under a reduced pressure of 1 atm or lower andconcentrated by low-temperature heating in a reduced-pressure state, andin each of said precipitation steps, said alcohol solution is added tosaid concentrated solution in said concentration step, and the resultantsolution is stirred and let stand for separation into a supernatantliquid portion and a precipitate portion at a ratio of 0.5:9.5 to2.5:7.5.